This invention relates generally to track apparatus for vehicles. In particular, this invention relates to track apparatus of the type for use in place of a vehivle wheel and, more particularly, to apparatus for maintaining proper tension on flexible tracks during operation.
Agricultural vehicles such as tractors, combines and the like are commonly used in agricultural fields for a variety of jobs, and construction vehicles and other large work vehicles are used for many different jobs on a variety of ground surfaces. Typically, these vehicles have tires on which the vehicles are supported on the ground. These kinds of large vehicles are quit heavy, and their weight is distributed to a relatively small area by the vehicle tires. As a result, the tires of such vehicles tend to compact the soil in the fields or other ground surfaces. Compacted soil discourages growth of crops planted in the fields with need loose soil to flourish, and ground surface compaction is often undesirable for other reasons as well.
In addition, since fields and other work sites are often wet due to rain or watering, vehicles which enter the fields become bogged down in the mud due to the fact that there is such a small area in contact with the ground. Therefore, it is highly desirable to develop a track apparatus for vehicles which spreads vehicle weight over a larger area so as to reduce the degree of ground compaction. Providing a larger ground-surface engagement area also serves to prevent vehicles from becoming bogged down in mud or other soft ground surfaces.
Prior track systems for vehicles is disclosed in U.S. Pat. Nos. Re36,284 (Kelderman) and 5,829,848 (kelderman), assigned to the assignee of the present invention and incorporated herein by reference. The Kelderman xe2x80x2284 reissue and xe2x80x2848 patents disclose track suspension systems for vehicles having a frame and a continuous rubber track. The drive wheel is attached to the frame for engaging and driving the continuous flexible track.
In order to insure proper operation of such track apparatus, the tension on the flexible track must be maintained within a predetermined range. Both a lack of sufficient tension and excessive tension are problematic.
By way of example, a minimum tension must be maintained on the flexible track to prevent slippage thereof during operation of the track apparatus -- i.e., inconsistent engagement of the track with leading and trailing idler wheels. Improper track tension is problematic in operation and leads to misalignment and premature wear of the flexible track may result in a loss of horsepower and premature wear of the track.
Furthermore, the flexible track of such track apparatus encounters obstacles (e.g. rocks) and other ground-surface irregularities during operation. It is important that the track accomodate irregularities and sudden shocks in order to maintain acceptable operational tension: (1) the matter of maintaining proper tension under normal operation conditions and (2) the ability to accommodate obstacles and the like.
While proper track apparatus have tensioning devices, such tensioning devices have problems and shortcomings in their ability to maintain proper tension in a wide variety of surface conditions. There is a need for improved tensioning apparatus to maintain proper track tension and better accommodate obstacles and a variety of surface irregularities during operation.
It is an object of this invention to provide an improved track apparatus, of the type for use in place of a vehicle wheel, which overcomes some of the problems and shortcomings of the prior art, including those referred to above.
More particularly, it is an ovject of this invention to provide an improved track tensioning apparatus which overcomes the problems and shortcomings of the prior art referred to abovr.
Another object of the invention is to provide a track apparatus which maintains a predetermined tension on the track in a variety of use conditions.
Another object of this invention is to provide a track tensioning apparatus which avoids or minimizes track xe2x80x9cslippagexe2x80x9d and misalignment during use.
Another object of the invention is to provide an improved track tensioning apparatus which better accommodates a wide range of track deflection of the track, caused by a variety of obstacles.
A still further object of the invention is to provide a track apparatus with a tensioning device which is simple, inexpensive to manufacture and maintain, and independent of the vehicle.
In accordance with the present invention, a tensioning device is provided for maintaining proper tension on a continuous flexible track utilized on a track apparatus of the type mountable on the rotatable axle of a vehicle.
The track apparatus includes: a frame; a drive wheel structure rotatably mounted with respect to the frame, the drive wheel having an upper circumferential portion engaging the inner surface of a flexible track along the upper length thereof and a lower circumferential portion spaced above the lower length of the track; and leading and trailing idler assemblies having idler wheels engaging the track. The tensioning device includes a dampening mechanism which extends betwee an idler assembly and the frame for exerting a force on the idler axle so as to urge the idler wheel towards the non-deflected position. The dampening mechanism provides force on the idler axle as the idler wheel moves towards the deflected position. The idler assembly includes an idler axle support pivotably mounted to the frame. The idler axle extends through the idler axle support.
The tensioning device of this invention includes a main-cylinder housing interconnected to the frame. The main-cylinder housing extends along an axis and defines a main cylinder chamber therein. A main position has a first end pivotably connected to the leading idler wheel assembly and a second end slidably received within the main-cylinder chamber. The main piston is movable between a first extended position in response to the idler wheel being in a non-deflected position and a second retracted position in response to the idler wheel being in the deflected position. A primary dampening structure discourages movement of the main piston toward the retracted position for a first predetermined axial length. A secondary dampening structure discourages movement of the main piston toward the retracted position for a second predetermined axial length.
The primary dampening structure includes a primary-dampening cylinder which extends along an axis and defines a primary chamber therein. A primary-dampening piston is slidably received within the primary-dampening cylinder and is movable axially between a first position and a second position. The primary-dampening piston divides the primary-dampening chamber into a first portion for receiving a pressurized gas and a second portion. A fluid conduit interconnects the second portion of the primary-dampening chamber and the main-cylinder chamber. A fluid is disposed within the second portion of the primary-dampening chamber; the main-cylinder chamber, and the fluid conduit therebetween.
Similarly, the secondary dampening structure includes a secondary-dampening cylinder extending along an axis and defining a secondary-dampening chamber therein. A secondary-dampening piston is slidably received in the secondary-dampening cylinder and is movable axially between a first position and a second position. The secondary-dampening piston divides the secondary-dampening chamber into a first portion for receiving a pressurized gas and a second portion. The fluid conduit also interconnects the second portion of the secondary-dampening chamber and the main-cylinder chamber. In addition, the fluid is also disposed in the second portion of the secondary-dampening chamber.
It is contemplated that the pressure of the pressurized gas in the first portion of the secondary-dampening chamber is greater than the pressure of the pressurized gas in the first portion of the primary-dampening chamber. A limiter may be provided within the primary-dampening cylinder for limiting movement of the primary-dampening piston.
The tensioning device may include a manifold having an input, a first output connected to the input of the secondary-dampening cylinder, and a second input connected to the input of the secondary-dampening cylinder. The fluid conduit interconnects the input of the manifold and the main-cylinder chamber. The fluid is disposed within the fluid conduit for travel between the second portion of the primary-dampening chamber, the second portion of the secondary-dampening chamber, and the main-cylinder chamber.
In accordance with a still further aspect of the present invention, the tensioning device a main cylinder housing interconnected to the frame of the track apparatus, such main-cylinder housing extends along an axis and defining a main-cylinder chamber therein. A main piston has a first end pivotably connected to the idler wheel and a second end slidably received within the main-cylinder chamber, and is movable between a first retracted position and a second extended position. A dampening mechanism which is mounted at a position remote from the main piston is operatively connected to the second end of the main piston and provides a force for discouraging movement of the main piston toward the retracted position. Such remote dampening mechanism progressively increases the force on a second end of the main piston as the main piston moves toward the retracted position. The remote dampening mechanism may include primary and secondary dampening as described above.
In accordance with a still further aspect of the present invention, a track apparatus is provided having the improved tensioning apparatus as described above.